1. Field of the Invention
This invention relates to an apparatus and a process for monitoring and/or providing a quantitative indication of insect infestations in stored products.
2. Description of the Prior Art
Protection of stored agricultural commodities from insect infestations and the direct loss caused by insects are costly. Insect infestations in stored agricultural commodities result in annual losses of millions of dollars. Early detection of infestation problems is necessary to initiate timely control measures and eliminate unnecessary "scheduled" insect treatments. Routine use of insecticides to protect stored products have many constraints.
The standard practice for detecting and quantifying infestation in stored grain is visual inspection of samples for adult insects. Insects are usually separated from grain samples with hand or inclined sieves. A traditional method of obtaining samples uses a long, hollow, multi-compartment grain trier inserted into the commodity. Its gates are then opened and closed to acquire samples at different depths and, after withdrawal, the samples are removed for inspection (Bauwin et at., In: Storage of Cereal Grains and Their Products; 2nd Ed., ed. C. M. Christensen, 115-157, 1974; St. Paul, Minn.: American Association of Cereal Chemists). Other methods can get beyond the limitation of only sampling close to the grain's surface. A vacuum probe can extract larger samples from deeper with a grain mass and a grain mass can be "turned" enabling a pelican sampler to catch samples from the moving grain stream (Noyes et at., In: Management of Grain, Bulk Commodities, and Bagged Products, Circular E-912, 71-79, Cooperative Extension Service, Oklahoma State University, 1991). None of these sampling techniques provide continuous and thorough monitoring. Low insect populations are difficult to detect in small samples and a much greater proportion of the grain needs to be sampled to accurately estimate insect population size (Hagstrum et at., In: Management of Grain, Bulk Commodities, and Bagged Products, Circular E-912, 65-69, Cooperative Extension Service, Oklahoma State University, 1991). Additionally, these sampling methods are expensive and labor intensive and therefore not repeated very often even though an infestation can grow from undetectable to damaging levels in two weeks. Another method, employed in some large grain elevators, is temperature sensing with thermocouple cables distributed throughout the storage volume. This system is only sensitive to very high insect populations. Furthermore, both moisture and mold growth can elevate temperature levels.
White et at. (Journal of the Kansas Entomological Society, Volume 63(4):506-525, 1990) and Reed et al. (Journal of Economic Entomology, Volume 84(4):1381-1387, 1991) both disclose passive grain probe traps that have been developed to address some of the shortcomings of the above methods. The probes are vertical perforated tubes that insects crawl into and then drop through to be trapped in a reservoir at the lower end. Probes are left in the grain for prolonged periods, allowing them to continuously capture insects and thus detect very low insect populations. However, the information is only available after the labor intensive process of inserting the trap into the grain, waiting, withdrawing the trap, and then inspecting the trap contents. The difficulty of insertion and withdrawal increases with the distance from the surface due to the resistance of the grain.
U.S. Patent No. 5,005,416 discloses an automated, continuous monitoring electronic grain probe trap with a bottom reservoir fitted with a detector that senses the movements of trapped insects. The number of insects caught in the trap is estimated based on the mount of vibration detected. However, temperature, species, time in the trap, the mount of food and other insects in the trap are all factors which can affect the trapped insects' vibration producing activity. Vibration detection may also be prone to error from ambient noise.
Hagstrum et at. (Proceedings 6th International Working Conference on Stored-Product Protection, Canberra, Australia, Volume I, pages 403-505, 1994) disclose a computer-based acoustic system that provides for automated monitoring by detecting insect generated sounds. Piezoelectric transducers, mounted on vertical cables installed in grain bins, sense the feeding and movement sounds of nearby insects. The acoustic sensor outputs are sequentially connected to electronic components that count and relay to a computer, the number of signal peaks crossing a threshold level during each sensor's observation interval.
While various systems for monitoring insect infestation of various stored agricultural commodities have been developed, there remains a need in the art for monitoring systems which provide automated realtime monitoring of insects. The present invention provides such an automated system which is different from prior art systems and solves some of the problems associated with prior art systems.